A manufacturing apparatus (manufacturing line) of a steel sheet by rolling has a step of spraying water over the steel sheet for the purpose of removing a scale formed and cooling the steel sheet having a high temperature. As is known, the spraying of water is carried out by means of a nozzle.
Patent Literatures 1 to 4 disclose techniques for incorporating a valve in each nozzle. By providing a valve for each nozzle, it is possible to separately choose a nozzle to spray water and a nozzle not to spray water. Accordingly, it is possible to inhibit an excessive water supply and water discharge, whereby it is possible to save energy and attain efficiency. Also, if a switching valve is provided for a large pipe provided on an upstream side which supplies water to the nozzle to thereby control water supply to the nozzle there, a shock, a so-called water hammer becomes large, which sometimes negatively affects the pipe and the like. By providing a valve for each nozzle, it is possible to inhibit the water hammer. To the valve used for a high-pressure pipe, sometimes a stellite build-up is applied in order to improve abrasion resistance property of the valve.